a) Field of the Invention
The present invention relates to a music box using pin wheels, and more specifically, to an anti-vibration damper which stops the vibration remaining in a reed immediately prior to its being picked.
b) Description of the Related Art
FIG. 7(a) shows essential sections of a disc music box as a representative model of music boxes using pin wheels. In disc music box 100, thin disc 102, on which projections 101 are cut out downward by a press process, is rotationally driven by a driving source (not shown in the figure) in the direction indicated by arrow R. Projections 101 are arranged on disc 102 to correspond to a music piece played by the music box. Also, projections 101 may be formed in forms shown in FIGS. 7 (b) and (c). In the body of the music box having disc 102, pin wheel unit 105, in which a plurality of pin wheels 104 are individually rotatable around fixed shaft 103 extended in the radial direction, and two combs 108a and 108b are placed. When disc 102 rotates in the direction indicated by arrow R, projections 101 engage pin portion 106 of pin wheel 104 placed within a moving path in which projections 101 moves such that pin wheels 104 are rotated in the direction indicated by arrow L by a predetermined angle. Thereafter, other pin portion 106, which is not engaged to projections 101, picks the reeds of combs 108a and 108b to generate sound.
FIG. 8 shows a body of a disc music box having a conventional structure; the following explains the disc music box for more detail using the figure. First comb 108a and second comb 108b, which comprise reeds 107a, 107b, respectively, having the same number as pin wheels 104, are placed in a predetermined position according to a musical scale on either side of pin wheel unit 105. More specifically, first and second combs 108a and 108b are fixed to base mount 109 wherein reeds 107a, 107b are arranged such that their ends can be disengaged from pin portions 106 of pin wheels 104.
Also, guide rollers 110 are placed at appropriate distance from each other around fixed shaft 103 of pin wheel unit 105 to support the bottom surface of disc 102. Guide rollers 110 sandwich disc 102 with pressing rollers 112 which are supported by disc pressing frame 111 above disc 102 and which are placed across from guide rollers 110. As a result, disc 102 is warped by a force acting thereat when projections 101 are engaged to pin portions 106 such that incomplete engagement is prevented.
Dampers 113a, 113b are formed on one side of each of pin wheels 104 in parallel to each other corresponding to reeds 107a, 107b, respectively, on either side; they are also fixed to base mount 109 via damper alignment rails 117a, 117b. Dampers 113a, 113b touch pin wheels 104 such that inertial movement is suppressed. Also, the dampers comprise stopper 114, which maintains the positional relationship of pin portion 106 to reeds 107a, 107b, and anti-vibration pieces 115a, 115b which stops vibration remaining in reeds 107a, 107b by contacting the sides of reeds 107a, 107b while the pin wheels are suspended.
Furthermore, convex portions, which interfere with the movement of pin portion 106, are formed on the surface of dampers 113a, 113b facing pin portions 106 by expanding the portions of 116a, 116b corresponding to the space between adjacent two pin portions 106 of pin wheels 104 during suspension of movement. The convex portions are pushed out of the moving path of pin wheels 104 by pin portion 106 when pin wheels 104 rotate. As a result, anti-vibration pieces 115a, 115b are displaced in continuous motion therein such that reeds 107a, 107b are released for free vibration.
This disc music box functions as follows. When disc 102 rotates, one of projections 101 is engaged to pin portion 106 in the moving path such that pin wheels 104 are turned. Then, immediately prior to picking of reeds 107a, 107b facing one of the two pin portions adjacent to the convex portions of dampers 113a, 113b, namely 106, which rotates ahead of another pin portion following pin portion 106, pushes the facing convex portions of dampers 113a, 113b such that reeds 107a, 107b are released from anti-vibration pieces 115a, 115b. Consequently, reeds 107a, 107b are picked by leading pin portion 106 such that reeds 107a, 107b freely vibrate to generate sound.
Pin wheels 104 stop rotation when their engagement is released by passing projections 101. Then, the convex portions of dampers 113a, 113b fall between following two pin portions 106 again such that vibration of reeds 107a, 107b is suppressed by anti-vibration pieces 115a, 115b which contact thereat. If vibration remains therein, the reeds contact the following pin portions to cause noise. In other words, dampers 113a, 113b are formed for the purpose of eliminating such noise due to the vibration remaining in reeds 113a, 113b.
Also, a damper may be fixed to a reed as shown in FIG. 9. In cylindrical music box 200, damper 202 made of a wire or a film is adhered underneath reed 201 which is firmly fixed to base mount 205. While cylinder 203 moves in the direction indicated by arrow C such that pin 204 shifts from pin position 204a to pin position 204c, the following operation takes place. At pin position 204b, which is a position immediately prior to picking of reed 201 by pin 204, the end of damper 202 is pushed up such that distortion caused in the wire or film of damper 202 lessens vibration; furthermore, the end of damper 202 contacts reed 201 such that vibration is stopped. Thereafter, pin 204 picks reed 201 and shifts to pin position 204c. As described above, damper 202 lessens/stops vibration of reed 201 immediately prior being picked by pin 204 such that noise including broken sound and the like is prevented.
Additionally, in disc music box 100, suppression of vibration remaining in reeds 107a, 107b is canceled immediately before the reeds are picked by pin portion 106, and vibration is stopped immediately after being picked such that reverberation is eliminated. On the other hand, in cylindrical music box 200, vibration is stopped immediately before pin 204 picks reed 201; reed 201 freely vibrates immediately after being picked such that reverberation exists.
In either of the above methods, dampers 103a, 103b or damper 202 are/is fixed. Therefore, pin wheels 104 or cylinder 203 contacts still dampers 103a, 103b or damper 202 during rotation such that braking force acts on pin wheels 104 or cylinder 203 due to friction resistance by contacting. As a result, large rotational torque is required for driving disc 102 or cylinder 203.
In disc music box 100, the shape of dampers 103a, 103b is complex and are fixed separate from reeds 107a, 107b and pin wheels 104; therefore, it is difficult to obtain precision in relative positions and sizes. Additionally, dampers 103a, 103b must be individually fixed while adjusting conditions of engagement of an individual damper corresponding to reeds 107a, 107b and pin portion 106; thus, more time is required for assembly, which is extremely inefficient.
Furthermore, for damper 202, as seen in cylindrical music box 200, sizes required for a length of the end part, the shape and a distance from reed 201 must be extremely precise. Also, it is difficult to obtain stability in preventing noise, in addition to difficulty in operation to fix damper 202 by adhesion. Moreover, when vibration energy is increased by thickening (or widening) reed 201 in order to improve acoustics, prevention of noise by stopping vibration of reed 201 may be incomplete unless the thickness of the film or diameter of the wire forming damper 202 is increased.
Moreover, when a thick film or a thick wire is used in damper 202, the film or wire of damper 202 moves away by being pushed by pin 204 such that noise tends to be generated due to elasticity of damper 202 thereafter. Also, a means in which damper 202 is fixed by directly adhering it to reed 201 may deteriorate sound qualities since a foreign object is adhered to the end of the damper due to the use of an adhesive.